Group messaging in HLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the main component responsible for storing group messages.

HLD

The component that stores all group messages is called the [1].

Drag options to blanks, or click blank then click option'

AMessage Queue

BAPI Gateway

CDatabase

DLoad Balancer

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing message queue with storage

Choosing load balancer as storage

The database is the main component that stores all group messages persistently.

2fill in blank

medium

Complete the code to specify the component that manages user connections in group messaging.

HLD

The [1] handles all active user connections and routes messages in real-time.

Drag options to blanks, or click blank then click option'

AWebSocket Server

BLoad Balancer

CCache

DDatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing database instead of connection manager

Confusing load balancer with connection handler

The WebSocket Server manages real-time connections and message routing between users.

3fill in blank

hard

Fix the error in the component responsible for message delivery to all group members.

HLD

The [1] is responsible for broadcasting messages to all members in a group.

Drag options to blanks, or click blank then click option'

ADatabase

BMessage Broker

CAPI Gateway

DLoad Balancer

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing database for message delivery

Confusing load balancer with message distributor

The Message Broker efficiently broadcasts messages to all group members in real-time.

4fill in blank

hard

Fill both blanks to complete the description of the system's scalability components.

HLD

To handle many users, the system uses [1] to distribute traffic and [2] to cache frequent data.

Drag options to blanks, or click blank then click option'

ALoad Balancer

BDatabase

CCache

DAPI Gateway

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up cache and database roles

Confusing API gateway with load balancer

Load Balancer distributes incoming traffic to multiple servers. Cache stores frequent data to reduce database load.

5fill in blank

hard

Fill all three blanks to complete the request flow in group messaging.

HLD

User sends message to [1], which forwards it to [2]; then [3] broadcasts it to group members.

Drag options to blanks, or click blank then click option'

AAPI Gateway

BMessage Broker

CWebSocket Server

DDatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping roles of message broker and WebSocket server

Choosing database as the broadcaster

The API Gateway receives the message, the Message Broker handles distribution, and the WebSocket Server broadcasts to connected users.

Practice

1. What is the primary purpose of a group messaging system?

easy

A. To allow multiple users to send and receive messages in a shared conversation

B. To store user passwords securely

C. To manage user profile pictures

D. To provide video streaming services

Solution

1. Step 1: Understand group messaging basics

   Group messaging connects multiple users so they can communicate together in one conversation.

2. Step 2: Identify the main function

   The main function is sending and receiving messages among group members, not unrelated features like password storage or video streaming.

3. Final Answer:

   To allow multiple users to send and receive messages in a shared conversation -> Option A

4. Quick Check:

   Group messaging = shared conversation [OK]

Hint: Focus on the core feature: multi-user message exchange [OK]

Common Mistakes:

• Confusing group messaging with unrelated features
• Thinking it only supports one-to-one chat
• Ignoring the shared conversation aspect

2. Which component is essential for managing who belongs to a group in a group messaging system?

easy

A. Group management

B. Notification service

C. Message storage

D. Media transcoding

Solution

1. Step 1: Identify components related to user membership

   Group management handles adding, removing, and listing members in a group.

2. Step 2: Exclude unrelated components

   Message storage saves messages, notification service alerts users, and media transcoding processes media, none manage group membership.

3. Final Answer:

   Group management -> Option A

4. Quick Check:

   Group membership = Group management [OK]

Hint: Group membership is handled by group management component [OK]

Common Mistakes:

• Confusing message storage with membership control
• Assuming notification service manages members
• Mixing media processing with group functions

3. Consider a group messaging system where each message is sent to all group members. If a group has 100 members and one message is sent, how many message deliveries occur?

medium

A. 1

B. 50

C. 101

D. 100

Solution

1. Step 1: Understand message delivery in group messaging

   Each message is delivered to every member of the group.

2. Step 2: Calculate total deliveries

   With 100 members, one message results in 100 deliveries (one per member).

3. Final Answer:

   100 -> Option D

4. Quick Check:

   Deliveries = group size = 100 [OK]

Hint: One message reaches all members, so deliveries = group size [OK]

Common Mistakes:

• Counting the sender as extra delivery
• Assuming half the group receives the message
• Confusing message count with delivery count

4. A group messaging system stores messages but users report delays in receiving messages. Which issue is most likely causing this delay?

medium

A. Message storage is too fast

B. Notification service is slow or failing

C. Group management is adding too many users

D. User profile pictures are too large

Solution

1. Step 1: Identify components involved in message delivery

   Notification service alerts users about new messages; if slow, users get delayed messages.

2. Step 2: Exclude unrelated causes

   Message storage speed does not cause delay in delivery; group management and profile pictures do not affect message delivery timing.

3. Final Answer:

   Notification service is slow or failing -> Option B

4. Quick Check:

   Delivery delay = notification issue [OK]

Hint: Delivery delays usually come from notification failures [OK]

Common Mistakes:

• Blaming message storage speed
• Thinking group size causes delay directly
• Ignoring notification service role

5. You are designing a scalable group messaging system for millions of users. Which approach best ensures message delivery without overloading servers?

hard

A. Send each message directly from sender to every recipient synchronously

B. Store messages only on sender's device and rely on manual forwarding

C. Use a message queue to asynchronously distribute messages to group members

D. Limit group size to 10 users to reduce load

Solution

1. Step 1: Understand scalability challenges

   Direct synchronous sending to many users overloads servers and causes delays.

2. Step 2: Identify scalable solution

   Using message queues allows asynchronous, reliable, and scalable message distribution without blocking sender or servers.

3. Step 3: Exclude impractical options

   Storing messages only on sender device or limiting group size reduces usability and scalability.

4. Final Answer:

   Use a message queue to asynchronously distribute messages to group members -> Option C

5. Quick Check:

   Scalable delivery = asynchronous queue [OK]

Hint: Use asynchronous queues for scalable message delivery [OK]

Common Mistakes:

• Trying synchronous delivery to all users
• Ignoring asynchronous processing benefits
• Reducing group size instead of scaling design